The overall goals of the proposed research are: 1) to investigate the decrease in concentration of triacylglycerols (TG) in rat plasma in response to physical exercise, and how this phenomenon is related to increase in lipoprotein lipase activity in the tissues; 2) to investigate, in vitro, the factors which participate in the regulation of muscle lipoprotein lipase activity. We plan to submit male and female rats to programs of acute and regular physical exercise and attempt to correlate the increases in the rate of their TG removal from the plasma to changes in muscle and adipose tissue lipoprotein lipase activity during starvation and post-prandially. In rats submitted to regular programs of physical exercise, muscle lipoprotein lipase activity is significantly increased compared to sendentary controls. The factors which regulate lipoprotein lipase activity in muscle of exercised or sendentary animals are not known. We plan to study the regulation of the muscle enzyme using the isolated perfused rat heart. With this system, which can be maintained metabolically active for long periods, we intend to examine the effects of serum, glucagon glucocorticoids and cyclic AMP on the enzyme activity.